1. Field of the Invention
The present invention relates to a spectrally sensitized silver halide photographic emulsion, and, more particularly, it relates to a silver halide emulsion supersensitized with a combination of two types of dimethinemerocyanine spectral sensitizers.
2. Description of the Prior Art
In some light-sensitive photographic materials such as high speed orthochromatic lith-type light-sensitive photographic materials, it has been required that the green-sensitivity be increased and the red-sensitivity be reduced.
It is generally known in the art that polymethinecyanine dyes such as cyanine, merocyanine, hemicyanine, etc. can be used for spectrally sensitizing a silver halide photographic emulsion. For example, in order to increase the sensitivity to light in the green spectral region, oxathiohydantoin dimethinemerocyanine dyes represented by the general formula (I) described hereinafter are known as disclosed in U.S. Pat. Nos. 3,384,486, 3,765,901 and 3,625,698, and Japanese Patent Publication No. 18105/71.
However, the green sensitivity of silver halide emulsion spectrally sensitized with the a spectral sensitizer of the general formula (I) is still practically insufficient.